1. Field of the Invention
The present invention generally relates to an optical disc drive apparatus and, more particularly, the optical disc drive apparatus of a type having a disc changer capability for recording and/or reproducing information on and from a selected one of a plurality of optical discs resting on drawable subtrays stacked on a main tray.
In particular, the optical disc drive apparatus of the present invention is suited for use in a personal computer and is so sized and so configured as to permit the replacement of the existing single disc drive in the personal computer.
2. Description of the Prior Art
With the advent of the age of personal computers, a CD-ROM drive has come into widespread use as a computer peripheral device and has now come standard with a majority of the computers. In addition, it is not rare for a single computer user to have a number of optical discs in possession. In this context, user demands are now increasing for CD-ROM drives having an automatic disc changing capability by which a plurality of optical discs can be loaded automatically one at a time to a position where access is made by an optical information read-out device, and also having a high speed information recording and/or reproducing capability which can be accomplished by, for example, increasing the speed of rotation of the optical disc.
On the other hand, in most of the desk-top personal computers, a CD-ROM drive or any other disc drive is installed in a housing space generally known as a "5-inch bay". The opening leading to this housing space is of a standard size generally known as a "5-inch half-height" size, and any peripheral device that is desired to be accommodated in the 5-inch bay must have a maximum size of 146 mm in width and 41.3 mm in height. Accordingly, the CD-ROM drive having a built-in automatic disc changer must also satisfy the size requirement if it be desired to be installed in the 5-inch bay. If indiscriminate design is made to allow the drive apparatus to accommodate an increased number of optical discs, the resultant drive would no longer satisfy the size requirement.
In any event, the CD-ROM drive having an automatic disc changing capability and satisfying the size and speed requirements, i.e., capable of being installed in the 5-inch bay is well known in the art. By way of example, the Japanese Laid-open Patent Publication No. 3-216857, published Sep. 24, 1991, discloses an optical disc drive apparatus comprising a main tray supported for movement between withdrawn and inserted positions relative to the drive housing and having a plurality of subtrays stacked thereon each for support thereon an optical disc. This optical disc drive apparatus is so designed that when the main tray is moved to the inserted position with the stacked subtrays held consequently at a stand-by position, a selected one of the subtrays then held at the stand-by position can be drawn towards a loaded position where the optical information read-out device makes access to the optical disc resting on such selected subtray.
According to this publication, the main tray is formed with grooves for holding the subtrays in equidistantly spaced relation to each other. When the optical disc resting on an arbitrarily chosen one of the subtrays then held at the stand-by position with the main tray held at the inserted position is desired to be removed or replaced with a different optical disc, the main tray carrying the entire number of the subtrays must be withdrawn to the withdrawn position so that the optical disc on the arbitrarily chosen subtray can be removed. After this removal has been made, the main tray must again be moved to the inserted position.
A similar optical disc drive apparatus is also disclosed in the Japanese Laid-open Patent Publication No. 6-259865, published Sep. 16, 1994. This known apparatus makes use of an elevating stocker positioned on one side of a disc playback position remote from the withdrawn position for the main tray and is so designed and so configured that, after a tray with a carriage or subtray thereon has been moved to the inserted position, the optical disc resting on the carriage or subtray is drawn to a playback position where it is played back. The optical disc having been played back is then transported together with the subtray towards the elevating stocker where it is accommodated. The stocker disclosed therein has a capacity of accommodating a plurality of, for example, 7, subtrays and, accordingly, by stacking the subtrays, each having an optical disc resting thereon, within the stocker, an arbitrarily chosen one of the subtrays can be drawn to the playback position that is defined intermediate between the inserted position for the tray and the stocker.
According to this second-mentioned publication, separate drive motors are required for driving the tray and for selectively lowering and lifting the stocker. In addition, the stocker is supported by a movable members and, therefore, when an impact acts on the apparatus during, for example, transport of the apparatus, not only may lifting pins be disengaged from the stocker, but also the movable member may be damaged.
The Japanese Laid-open Utility Model Publication No. 5-96936, published Dec. 27, 1993, discloses the design in which the space between the neighboring subtrays stacked on the main tray, which is exhibited when the main tray is moved to the stand-by position, is minimized to render the apparatus as a whole to have a reduced height, but in which the space between the neighboring subtrays, which is exhibited when the subtray positioned between those neighboring subtray has been moved to the loaded position with a part thereof situated between such neighboring subtrays, is expanded to allow the optical disc to be rotated within such space.
A combination of the Japanese Laid-open Patent Publications No. 9-7281, published Jan. 10, 1997; No. 9-44962, published Feb. 14, 1997; No. 9-91834, published Apr. 4, 1997; and No. 9-139004, published May 27, 1997, which corresponds to the U.S. patent application Ser. No. 08/670,100 filed Jun. 25, 1996 and assigned to the same assignee of the present invention, the disclosure of which is herein incorporated for all purposes of the present invention, discloses an optical disc drive apparatus including a main tray having a stack of subtrays mounted thereon and movable between withdrawn and inserted positions, means for moving the main tray from the withdrawn position towards the inserted position, means for drawing an arbitrarily chosen one of the subtrays from a stand-by position towards a loaded position defined above a traverse plate or clamp support plate while the main tray is held at the inserted position, a clamp device including a clamper for clamping an optical disc resting on the subtray then drawn to the loaded position between the clamper and a turntable on the traverse plate for rotation together therewith, and an elevating means including an elevating table for selectively lifting and lowering the loading drive means in a direction in which the subtrays are stacked on the main tray so that the arbitrarily chosen subtray may be drawn from the stand-by position towards the loaded position.
With this design, when an optical disc resting on one of the subtrays other than the uppermost subtray then held at the loaded position is desired to be removed or replaced, not only can such one of the subtray be returned smoothly from the loaded position to the stand-by position, but the main tray is allowed to withdraw from the inserted position back to the withdrawn position carrying such one of the subtrays and the subtray or subtrays positioned immediately thereabove while leaving the subtray or the subtrays positioned above such one of the subtrays at the stand-by position in a substantially horizontal posture, so that such one of the subtrays can readily be exposed to the outside for removal or replacement of the optical disc resting thereon.
The optical disc drive apparatus disclosed in the above mentioned US application is satisfactorily designed and configured so as to meet the size requirement, i.e., capability of being installed in the 5-inch bay in any existing computer, and also to meet the speed requirement. However, the optical disc drive apparatus of the U.S. Ser. No. 08/670,100 has subsequently been found having improvements to be done for the purpose of accomplishing a highly reliable information recording and/or reproduction.
More specifically, the turntable, a spindle drive motor for driving the turntable, an optical pick-up and the traverse plate or clamp support plate supporting thereon those component parts are supported by the elevating table for movement up and down relative to the chassis. The elevating table is elevatable in a vertical direction substantially parallel to the plane of rotation o the optical disc between a lowered position and an elevated position.
In order to permit the optical pick-up to read information from the optical disc on one of the subtrays which has been moved from the stand-by position to the loaded position, the turntable and the traverse plate angularly movable up and down about clamp support pins serve to lift the optical disc above the subtray to allow the optical disc to be clamped between the clamper and the turntable in readiness for the drive of the optical disc in one direction by means of the spindle drive motor.
In other words, the traverse plate having the turntable mounted thereon has a rear end pivotally connected to the clamp support pins that define a common axis about which the traverse plate can be pivoted. This traverse plate is retained by the elevating table movable up and down within the chassis so that when the elevating table moves up and down, the traverse plate can be pivoted about the common axis connecting between the clamp support pins. When the optical disc on any one of the subtrays is to be moved from the stand-by position towards the loaded position or from the loaded position towards the stand-by position, the traverse plate is pivoted in one direction with its front end lowering to provide a space above the turntable through which the optical disc can be moved without being hampered by component parts positioned therearound. On the other hand, when the optical disc on any one of the subtrays is to be reproduced, the traverse plate is pivoted in the opposite direction with the front end thereof lifted so that the optical disc moved to the loaded position from the stand-by position can be clamped between the clamper and the turntable.
The pivot of the traverse plate is accomplished when the clamp device driven by a drive motor through a drive transmission mechanism such as a train of gears acts on the traverse plate. In this suggested disc drive apparatus designed to accommodate the optical discs as many as possible within the maximum available volume of the disc chamber together with the main tray and the associated subtrays, the clamp device has to be disposed at a position laterally offset from the optical disc held at the loaded position, that is, at a position sufficient to permit the clamp device to act on either a left side wall or a right side wall of the traverse plate so that it will not interfere with the optical disc then held at the loaded position.
Where the point of the traverse plate on which the clamp device acts to pivot the traverse plate is defined at the position offset laterally from a relatively heavy component part such as the turntable and the spindle drive motor, for example, at the right side wall of the traverse plate, it may occur that the traverse plate when being angularly moved by the action of the clamp device about the common axis between the clamp support pins may be deformed, i.e., skewed or tilted sidewise because of a bias of load imposed on the right side wall of the traverse plate. In other words, when the traverse plate is being pivoted while the clamp device acts on the right side wall of the traverse plate, the traverse plate will be pivoted having been skewed relative to a plane of rotation of the optical disc.
Because of the skew tending to occur during the pivotal movement of the traverse plate, the turntable mounted on the traverse plate correspondingly tilts. Once this occurs, the optical disc clamped between the turntable and the clamper will undergo a fluctuated rotation about the spindle, making it difficult for the optical pick-up assembly to read information accurately from the optical disc.
Also, where the information reading speed is to be increased to meet the market demands, the speed of drive of the optical disc must be increased. However, by the reason associated with manufacture of optical discs and/or by reason of change in environment, some of the optical discs manufactured may have a center hole slightly offset from the position where it ought to occupy and/or a bias in mass distributed circumferentially thereof, a high speed rotation of the optical disc will bring about a relatively large centrifugal force. The larger the centrifugal force, the more considerably the traverse plate is vibrated. This is because of the presence of a gap between the chassis and the elevating table supporting the disc clamp device and the traverse plate. The presence of the gap tends to allow the elevating table 40 to undergo a repeated lateral displacement relative to the chassis under the influence of such relatively large centrifugal force. This problem also results in failure of the optical pick-up assembly to accomplish an accurate reading of information from the optical disc.